Mechanical properties of biliary metallic stents: an experimental comparison

To assess the physical properties of biliary self-expandable metallic stents. Six different types of biliary self-expandable metallic stents (Wallstent, ZA stent, Accuflex, S.M.A.R.T. stent, Spiral Z stent, and NT stent) were evaluated for the flexibility, trackability, and resistance of stent release for the introducer, and for repulsion force, flexibility, radial force, radio-opacity, and kink resistance for the stent. The Wallstent showed the best repulsion force, radio-opacity, and kink- resistance, while the ZA stent showed the best flexibility and trackability of the introducer and better radial force and radio-opacity. Accuflex showed the least resistance during stent release and better flexibility and radial force. The S.M.A.R.T. stent showed the largest radial force, and the Spiral Z stent showed better trackability of the introducer and better radio-opacity. The NT stent seemed to require overall improvement. The Wallstent appears preferable for placement in the extrahepatic bile ducts. The ZA stent can be applied for various approaches, but placement in comparatively straight bile ducts is preferable. With the Accuflex, insertion through routes where an acute angle exists should be avoided. In addition, balloon expansion before or after stent placement is preferable. The S.M.A.R.T. stent is placed in straighter intrahepatic bile ducts, while the Spiral Z stent should be placed through a straight approach. Balloon expansion before or after stent placement is preferable for the NT stent. No stent exhibited all of the ideal properties required. These results may contribute to the selection of biliary metallic stents.